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The Space Shuttle Program still can surprise engineers and technicians, even after 117 flights.

And the engineers have proven up to the task, even if it means building unique tools to handle the situation.

The latest example came from a freak hail storm that hit shuttle Atlantis while it sat on Launch Pad 39A at NASA's Kennedy Space Center in Florida. The hail dinged the foam on the external tank, setting off an unprecedented repair effort.

Image right: Lockheed Martin tool designers designed and built this specialized sander in 10 days. One part fits over the top of the external tank and the other holds the sander to smooth tank foam. Photo credit: NASA/ Jack Pfaller

"My first impression was, 'Oh, I guess they're going to exchange the tank and send it back to Michoud,' " said Glenn Lapeyronnie, a mechanical engineer at Lockheed Martin's external tank factory in Michoud, La.

NASA returned Atlantis to the Vehicle Assembly Building and began inspections. Soon, the engineers decided the damage was not as bad as they thought. But they knew extensive repairs would still be needed, along with some new instruments. Another consideration: The work would be done at Kennedy, with the tank still standing vertically.

Although some work on the foam is performed at Kennedy, it is normally limited to hand spraying foam onto small areas of the tank. The repairs the hail damage called for had not been done before at the Florida launch site.

Image left: The sander had to be mounted just right so it would sand the external tank smooth without leaving waves on uneven lumps. Photo credit: NASA/ Jack Pfaller

"We needed a tool to go do this," Lapeyronnie said. "This was not going to be a hand-spraying job."

Lapeyronnie and the tool design group at Michoud were given a list of specifications and set out to build a tool that would sand down the foam at the top of the tank. The sanding would smooth the foam that Kennedy workers were spraying onto the damaged area. Sprayed foam leaves a bubbled surface that would not pass inspections, so the sanding was a necessity.

"We have a tool that does this in the manufacturing and production line," Lapeyronnie said, "(but) it is a lot different because the spike, the nosecone, the cable tray, none of that is in place on the production line."

About 10 days after getting the specs, the Lockheed Martin engineers had their instrument designed and built. Later, it would get a nickname: the pencil sharpener.

The aluminum device fits on a conference table and weighs almost 100 pounds. One end is designed to fit over the spike at the top of the tank, while the other end holds a 2-foot-long cylinder of sandpaper that grinds the foam flat. Two technicians operate the device, slowing sanding away a tenth-of-an-inch of foam at a time until the tank tip looked as good as new.

Atlantis was able to roll out to the launch pad again and is poised to make its climb into space riding the repaired tank.